原发性肉碱缺乏致脂质沉积性肌病的临床与病理特点

目的 分析原发性肉碱缺乏致脂质沉积性肌病（LSM）的临床与病理特点。方法 回顾性分析4例可能LSM患者的临床资料。结果 本组患者为亚急性或慢性起病，主要表现为近端肌无力，疲劳不能耐受；血清肌酶有不同程度的升高；肌电图示肌源性损害；病理检查示肌纤维内可见大量细小空泡和裂隙形成；MGT染色无破碎红纤维，油红O染色显示空泡为大量脂滴充填；受累纤维以Ⅰ型纤维为主。电镜证实肌纤维内脂滴堆积，可伴有线粒体的轻度增多。改善能量和糖皮质激素治疗有效。结论原发性肉碱缺乏致LSM是一种以易疲劳和肌无力为主要临床表现的脂质代谢障碍性肌病，病理改变以肌纤维内脂滴堆积为主，一般不伴有线粒体结构的明显异常。糖皮质激素治疗可获得良好疗效。     

脂质沉积性肌病的临床和病理特点

目的总结脂质沉积性肌病（lipid storage myopathy,LSM）的临床和病理特点,为早期诊断和治疗提供参考。方法对5例脂质沉积性肌病患者的临床资料进行回顾性分析。结果 5例脂质沉积性肌病患者均为慢性或亚急性起病,主要表现为不同程度的肌无力和对运动不耐受、血清肌酶均升高、神经电生理检查显示肌源性损害,病理检查发现肌纤维内空泡样变,脂滴明显增多,脂滴空泡呈＂串珠＂样排列。给予能量支持、低脂饮食、糖皮质激素等治疗后患者的临床症状好转。结论脂质沉积性肌病的确诊依靠肌肉活检,该病预后良好,及时的诊断和综合治疗可明显改善患者的生活质量。     

Mitochondrial myopathy with dystrophic features due to a novel mutation in the MTTM gene

Introduction: A 61‐year‐old woman with a 5‐year history of progressive muscle weakness and atrophy had a muscle biopsy characterized by a combination of dystrophic features (necrotic fibers and endomysial fibrosis) and mitochondrial alterations [ragged‐red, cytochrome c oxidase (COX)‐negative fibers]. Methods: Sequencing of the whole mtDNA, assessment of the mutation load in muscle and accessible nonmuscle tissues, and single fiber polymerase chain reaction. Results: Muscle mitochondrial DNA (mtDNA) sequencing revealed a novel heteroplasmic mutation (m.4403G>A) in the gene (MTTM) that encodes tRNA^Met. The mutation was not present in accessible nonmuscle tissues from the patient or 2 asymptomatic sisters. Conclusions: The clinical features and muscle morphology in this patient are very similar to those described in a previous patient with a different mutation, also in MTTM, which suggests that mutations in this gene confer a distinctive “dystrophic” quality. This may be a diagnostic clue in patients with isolated mitochondrial myopathy. Muscle Nerve 50:292–295, 2014     

Clinical and pathological heterogeneity in late-onset partial merosin deficiency

Mutations in the LAMA2 gene result in a complete loss of merosin and underlie a severe congenital type of muscular dystrophy (MDC1A).We investigated the clinical, genetic, and histological basis of late-onset muscular dystrophy in one family. The proband and her affected brother exhibited late-onset predominantly proximal muscle weakness. In addition, the proband experienced seizures. Magnetic resonance imaging of her brain demonstrated white-matter abnormalities. Sequencing of LAMA2 identified two new heterozygous point mutations in the two affected members. Muscle histology demonstrated dystrophic features, rimmed vacuoles, and partial loss of laminin α immunoreactivity. Partial merosin deficiency can present with a mild, late-onset limb-girdle-type pattern of weakness, with or without epilepsy, and pathologically may exhibit features observed in inclusion-body myopathy.     

Serial brain imaging analysis of stroke-like episodes in MELAS

We report 2 patients of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and consider the pathophysiology of stroke-like lesions, using magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) on MRI, perfusion imaging on MRI, and 1H magnetic resonance spectroscopy (1H-MRS). In Patient 1, T2-weighted imaging (T2-WI) on MRI at onset and even at 44 days after onset of the stroke-like episode showed high intensity in left parietal, temporal, and occipital lobe lesions. In the temporal lobe lesion, the apparent diffusion coefficient (ADC) at 44 days after onset was higher (average: 1.219x10(-3)mm2/s) than that in a normal region (average: 0.796x10(-3)mm2/s). (1)H-MRS of the left parietal lobe lesion at the same day showed a decrease in N-acetylaspartate/(creatine+phosphocreatine) (NAA/Cr) (0.43) and a peak in lactate. 1H-MRS of the contralateral side at the same day showed NAA/Cr (1.57) and no peak in lactate. Thereafter, ADC gradually decreased and NAA/Cr gradually increased, and the peak in lactate disappeared in the lesion. In Patient 2, T2-WI at onset showed high intensity in bilateral occipital lobe lesions. In the left occipital lobe lesion, ADC at the same day was higher (1.082x10(-3)mm2/s) than that in a normal region (average: 0.841x10(-3)mm2/s). (1)H-MRS of the left occipital lobe lesion at the same day showed a decrease of NAA (3.0mM) and a peak in lactate (13.1mM) (measured by LCModel). In 1H-MRS of the normal left parietooccipital lobe at 4 months before onset, NAA was 7.6mM and there was no peak in lactate (0mM). Perfusion imaging at onset showed high intensity in bilateral occipital lobes, which indicated hyperperfusion in stroke-like lesions. Thereafter, ADC gradually decreased and the peak in lactate partially decreased, and the low concentration of NAA persisted (regardless of the partial recovery) in the lesion. These results suggest that the stroke-like episodes is related to vasogenic edema, hyperperfusion, and neuronal damage. Acute oxidative phosphorylation defect may have a crucial role in the pathophysiology of stroke-like episodes.     

Abnormal distribution of desmin and vimentin in myofibers in adult onset myotubular myopathy.

We report, for the first time, muscle immunocytochemical studies in sporadic, adult onset myotubular myopathy (SAOMM), which show intramyofibrillar central, perinuclear desmin and vimentin. This pattern was absent in a normal control and in myofibers with increased internal nuclei associated with denervation and myotonic muscular dystrophy (MyD). These findings resemble those reported in 8- to 15-week-old human fetal myotubes and myofibers of infantile MM, implying a possible regression of intermediate filaments of adult myofibers to an early developmental phase in SAOMM.     

Molecular diagnosis of inheritable neuromuscular disorders. Part I: Genetic determinants of inherited disease and their laboratory detection

Understanding of the genetic basis of inheritable neuromuscular disorders has grown rapidly over the last decade, resulting in improved classification and understanding of their pathogenesis. A consequence of these advances has been the development of genetic tests of blood specimens for the diagnosis of many of these diseases. For many patients, these blood tests have eliminated the need for other more invasive diagnostic tests such as muscle or nerve biopsy, and for some patients, reduced exposure to immunosuppressive medication and its complications. The first part of this review focuses on the nature of genetic disorders, the laboratory methods used in the performance of genetic tests, and general practical aspects of their use and interpretation. The second part discusses the applicability of these tests to the range of neuromuscular disorders.     

Muscle fibre type composition in distal myopathy (Welander). An analysis with enzyme- and immuno-histochemical, gel-electrophoretic and ultrastructural techniques

The myopathic muscle of distal myopathy (Welander's disease), the dominantly inherited neuromuscular disorder which occurs frequently in Sweden, has been characterized by electron microscopy, enzyme- and immuno-histochemistry (using antibodies against embryonic, neonatal, fast and slow myosin, and against the muscle-specific intermediate filament protein, desmin), and with gel electrophoretic techniques. Of special interest is the fact that the ultrastructural appearance of the fibres with regard to M- and Z-band structures does not fit the proposed classification criteria for ultrastructural fibre typing of normal human muscle. Furthermore, contrary to previous results, we conclusively demonstrate that the predominating fibres are of a slow-twitch type. Unexpectedly, we also observed that embryonic and neonatal myosin was expressed in some residual fibres. This emphasises the importance of supplementing stains to demonstrate activity of ATPase with myosin immuno-histochemistry in order to improve understanding of fibre type characteristics in myopathic muscles. The origin of the myopathic muscle fibres in distal myopathy could not be definitely determined, but it is suggested that neurogenic disturbances play an important part in the pathophysiology of Welander's disease.